During the course of a surgical operation on a patient, it is often necessary to remove various body fluids, including blood, from the site of the operation. Removal and collection of such body fluids is generally accomplished using a suction receptacle connected to a vacuum source to draw the fluids through a tube for deposit and collection in a fluid collection receptacle.
Typically, suction systems utilize a fluid collection receptacle and a cover which are secured together in a fluid tight fashion. Two connections are provided in the cover, one to be connected by a tube to the source of vacuum, for example, a vacuum pump or hospital vacuum outlet station. The other connection is connected through a drainage tube to the particular area of the patient requiring drainage. The vacuum pressure applied to the receptacle carries fluid through the drainage tube to a fluid inlet port in the receptacle cover.
Fluid receptacles typically utilize a float assembly or shutoff valve positioned in line with the vacuum source. The shutoff valve is operable to close the vacuum source inlet port when the fluid collected in the receptacle rises to a predetermined level. As will be subsequently described, care must be taken to prevent premature closing of the vacuum source inlet port.
It has been found that during normal operation of a fluid collection receptacle, a substantial amount of aerosol droplets and particles are created by the force of the fluid entering the receptacle. In prior collection receptacles, these aerosol particles can be entrained in the air within the system to be drawn out the vacuum port and deposited in the vacuum tubing, regulators and the vacuum source. Such aerosol particles are not only dangerous because they can carry bacteria and the like, but the particles can also cause corrosion and other damage to the vacuum regulators and the vacuum system itself.
The fluid entering suction receptacles typically has a pH level considerably different than water. Stomach acids and body fluid pH levels can range from 3.5 to 3.9, while irrigating fluid pH levels may range from 8 to 10. Additionally, chloride salts and emesis enter suction receptacles. The presence of this high pH material causes severe corrosion of vacuum regulators. Since needle valves of many such regulators are made from turned brass, the presence of this fluid has a highly corrosive effect, causing pitting of the valve and clogging which prevents the valve from shutting off. Additionally, regulator diaphragms are typically made from neoprene rubber which is affected by the salts present in fluid entering the vacuum port from suction receptacles. These salts can cause the diaphragm to lose its resiliency and crack, such that the regulator loses its ability to smoothly operate between full on and off positions. Entrained particles can also clog the inlet and outlet opening to the regulators associated with suction systems.
The collection of fluids and materials in such regulators further provides a source of nutrients for bacteria and the regulators become a breeding ground for bacteria that can be transmitted to the patient, hospital personnel and all those in the vicinity of the regulators.
Numerous previously developed suction systems have employed shutoff valves which attempt to prevent the passage of fluid while permitting gases to pass to the source of vacuum. Such prior art systems are generally categorized as being hydrophobic in that hydrophobic filters are utilized in such systems. A hydrophobic filter is one generally categorized by being nonreactive with the liquids that it filters and is composed of material having discrete small holes which prevent the passage of water therethrough. Hydrophobic filters thus filter out aerosol droplets but do not absorb the liquid. As an illustrative example, a hydrophobic filter may be viewed as a woven fine mesh of screen such that particles larger than the mesh size are filtered. In such a hydrophobic filter, water is filtered and tends to accumulate on the surface of the filter, thereby clogging the apertures in the filter and preventing the passage of air through the filter. A typical problem thus associated with hydrophobic filters utilized in suction systems is that, due to the presence of aerosol droplets within the suction system, these aerosol droplets collect on the hydrophobic filter and cause unintentional cessation of the vacuum applied to the suction receptacle such that premature shutoff occurs. Such premature vacuum cutoff can be very dangerous during an operation. Prior art filters were therefore primarily intended for use as shutoff valves in case of fluid overflow and were not intended or effective for preventing aspiration of aerosol droplets into the vacuum line.
Generally representative of previously developed suction systems which have employed hydrophobic shutoff valves are described in U.S. Pat. No. 3,719,197 issued to Pannier, Jr., et al on Mar. 6, 1973 and entitled, "Aeseptic Suction Drainage System and Valve Therefor", U.S. Pat. No. 3,738,381 issued to Holbrook on June 12, 1973 and entitled, "Inverted Fluid Collection Receptacle" and U.S. Pat. No. 4,013,076 issued to Puderbaugh, et al on Mar. 22, 1977 and entitled "Aspirator Jar". The devices described in these patents employ hydrophobic filters to exclude the passage of fluid from the vacuum line in an overflow condition. Prior suction systems have also utilized filters in the form of screens to collect large particles such as bone fragments and chips to prevent these particles from entering the vacuum line. Such a device is described in U.S. Pat. No. 3,965,902 issued to Reilly, et al on June 29, 1976 and entitled "Disposable Fluid Collection Container". The device disclosed in the Reilly patent was manufactured and sold by Respiratory Care, Inc. of Arlington Heights, Ill. under the trade name Evacupak.
Numerous other suction systems have been manufactured and sold generally categorized as utilizing hydrophobic filters including products manufactured by Sorenson Research Company of Salt Lake City, Utah under the trade name Vac-Gard, British Oxygen Company, Ltd. of Essex, England under the trade name BOC Medishield, Air Products of Allentown, Pa. manufactured under the trademark MELCO MED, Medi-Vac Corporation of Abilene, Tex. Model No. 828014 External Aerosol Trap and products manufactured by Oxequip Health Industries of Chicago, Ill. and Vernitron Medical Products, Inc. of Carlstadt, N.J. In addition, hydrophobic filters constructed from paper have been previously developed. Hydrophobic filter suction systems have thus not been satisfactory in preventing the passage of aerosol particles into vacuum regulators and the vacuum system itself during the entire operation of the suction systems, while also giving overflow protection.
Other types of filters have also been developed for medical suction environments, but none have provided the necessary filtering of fluid and particles from the vacuum line without causing premature shutoff of the vacuum system. For example, it has been proposed to provide particulate filters incorporating natural fibers such as cotton between the suction collection canister liquid level and the suction shutoff valve. Such filters are rendered useless in an overflow condition and could allow the passage of both liquid and particles into the vacuum system prior to actual shutoff. Moreover, such natural fibers require relatively large and cumbersome filter packages and cannot maintain the desired shape, thereby tending to allow substantial air leaks at the filter periphery and at other locations. Such air leakage is magnified if such natural fibers become wet, as the fibers then tend to lose shape and actually migrate, causing even greater air leaks. Such air leaks allow direct passage of liquid and particles into the vacuum systems, thereby creating the problems previously mentioned.
A need has thus arisen for a device for use in combination with a vacuum shutoff valve which prevents the passage of fluid into the vacuum line of suction systems, but which does not cause a premature actuation of the shutoff valve to stop the flow of vacuum pressure to the suction receptacle. A need has further arisen for a device which will continually maintain its filtering integrity for preventing nutrients, bacteria and chemicals from entering regulators of vacuum sources for suction receptacles during extended use of the filter. A need has further arisen for a device that is independent of a vacuum shutoff valve to function as a filter for the vacuum line to filter bacteria nutrients, solid particles, bacteria, chemicals and aerosol particles from entering the vacuum line and regulators of suction systems.